Distribution characteristics of nitrogen and phosphorus in mining induced subsidence wetland in Panbei coal mine, China

Coal mining subsidence forms anthropogenic wetland. Nutrients in cropland around the wetland will be transferred into catchment along the slope of the coal mining wetland especially by the water washing in raining season. On the other hand, the washed nutrients from the cropland will be accumulated in the sediments of the catchment and eutrophicate the water body of catchment potentially. Nitrogen and phosphorus were selected as the biogeochemical indicators to address the environment effect of coal mining subsidence wetland in Panbei Coal Mine, Huainan, China. Nine water samples, nine sediment samples in the catchment, and twenty-seven topsoil samples around the catchment were collected. Contents of total nitrogen (TN), NO3-N, NH4-N, total phosphorus (TP) and available phosphorus of water, sediment and topsoil in coal mining subsidence wetland were measured. Distribution characteristics of nitrogen and phosphorus contents in water, sediments and topsoil in coal mining subsidence wetland indicated that their contents in water were relative lower, and highest contents in sediments were found, which reflected the nutrient absorption and accumulation in the sediment. In Panbei coal mining, the characteristics of distributions of nitrogen and phosphorus contents in topsoil of coal mining wetland generally decreased along the slope from flooded area to top of the basin. The phenomena indicated that the gradient formed by coal underground mining led to the nutrient losses in cropland and nutrient accumulaiton in sediments of catchment.